Are populations of Polylepis australis locally adapted along their elevation gradient?

ABSTRACT

Mountain ecosystems are characterized by steep environmental gradients. Species with broad elevation distribution are exposed to contrasting climatic conditions along their gradients. In response to those changes, species might develop ecotypes adapted to the local climate. Early regeneration is the most critical stage for plant populations and, therefore, withstands strong selection pressures. Previous studies showed a unimodal pattern of intraspecific variability in fitness components among Polylepis australis populations along their elevation gradient in the mountains of central Argentina. Whether this variability is the result of local populations’ adjustments to their respective site remains unknown. We tested the hypothesis that P. australis populations from different elevations would be locally adapted to their local environments, where they would perform better than populations from other elevations (origins). We applied an experimental approach by establishing common gardens at three contrasting elevations. Seeds and saplings of P. australis populations from the low, mid- and high elevation belts of the species distribution gradient (i.e. three origins) were reciprocally sown and transplanted in three elevation sites (low, mid- and high). Seed germination success, sapling growth and mortality were monitored for three years. Our main results show that the origin of populations influenced germination success and sapling growth, whereas sapling mortality was marginally affected. Populations of both elevation extremes seem to be more adjusted to local conditions than the population from the intermediate elevation, probably due to the harsher environmental conditions for plant regeneration typical of the lower and upper elevation belts of semiarid mountains. Finally, our results strongly suggest that temperature rise due to climate change in this mountain area might have negative effects on the regeneration of P. australis populations.

KEYWORDS:

• Argentina
• climate change
• regeneration
• tree species
• semi-arid mountains

Acknowledgments

This work was supported by the German Research Foundation (Deuthsche Forschungsgemeinchaft Grant/ Award Number: HE3041/21-1), and SECyT (05/1781 and 30720150101020CB). Special thanks to colleagues and students that collaborated during sapling transplants and field measurements: MR Rosetti, N Kushmanish, LD Gorné, MA Giorgis, AI País-Bosch, AM Rubini-Pisano, J Meneghello, G González, D Simian. Additionally, we are thankful to owners that permitted us to establish common gardens in private properties. AG got a research assistant position at FCEFyN (UNC) to participate in this project (Resolution 330-H.C.D.-2018). We also wish to thank two anonymous reviewers for useful comments on the manuscript and to Jorgelina Brasca who assisted with the English editing.

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).

Geolocation information

The study was conducted near the Linderos road (S32° 53ʹ W64° 3ʹ), in Sierras Grandes, Córdoba, Argentina.

Additional information

Funding

This work was supported by the Deuthsche Forschungsgemeinchaft [HE3041/21-1]; Secretaria de Ciencia y Tecnología - Universidad Nacional de Córdoba [SeCyT: 30720150101020CB]; Secretaria de Ciencia y Tecnología - Universidad Nacional de Córdoba [05/1781].